MPEG Compliant Streams
Methods and systems for compressing and transmitting media signals are known in the art. Compressed digital video is largely becoming the preferred medium to transmit to video viewers everywhere. Part of the Moving Pictures Experts Group (MPEG) specifications are standardized methods for compressing and transmitting video. In general, MPEG is used today for transmitting video over terrestrial, wireless, satellite and cable communication channels and also for storing digital video.
A video stream is usually organized as an ordered sequence of pictures. Each picture includes a plurality of slices, each slice including a plurality of macro-blocks. Macroblock can include a macro-block header and information representative of a group of pixels. The group can include an array of 16×16 pixels but this is not necessarily so. The micro-block header includes various fields such as an address of the macro-block in an image, a macro-block type (macro-block belongs to a I-picture, P-picture or B-picture), quantization scale value (usually included if the quantization scale value differs from the quantization scale value of a previous macro-block) and Coded Block Pattern field.
Audio and video streams are provided to an audio encoder and video encoder respectively to generate compressed audio and video elementary streams, also referred to as elementary streams.
A video elementary stream includes a video elementary stream payload. This payload may include pictures. Each picture includes slices and each slice includes macro-blocks. A slice includes a slice header that in turn includes slice type, buffer parameters and encoding parameters.
Elementary streams are packetized to produce PES packets. PES packets made up of elementary streams that form a program share a common time base. The PES packets may also include additional information. PES packets of distinct elementary streams can be arranged as a Transport Stream.
A Transport Stream combines one or more programs with one or more independent time bases into a single stream. Transport Streams include Transport packets of 188 bytes. Transport Stream packets start with a Transport packet header. The header includes a packet identifier (PID). Transport Stream packets of one PID value carry data of a single elementary stream. The packet identifiers are used by user devices to filter selected streams (relating, for example, to a certain television channel to which the user wishes to be tuned to) out of the Transport Stream.
Image Navigation
Due to bandwidth constraints, processing constraints (usually of user computers) and, additionally or alternatively, memory limitations, users can receive a limited amount of information via a network such as a cable network. Users would like to navigate between portions of a large image, without downloading the whole large image to their computer.
There is a need to provide an efficient method and system for providing visual content to a user.